Poly(ethylene terephthalate) fibers accounts for the main part of the polyester applied by the textile industry. The fibers are produced by e.g. poly-condensation of terephthalic acid and ethylene glycol, and drawing of fibers from a melt.
Because of its strength, polyester fabrics and/or garments are subject to pill formation, and possibly the most important of the cloth-finishing processes applied to polyester staple-fibre materials are those designed for control of pilling. All staple-fibre materials tend to form small balls or "pills" of entangled fibres at the cloth surface, when subjected to mild abrasion during wash and wear. If the fabric contains a substantial proportion of fibres having high resistance to flexural abrasion, the pills may be retained on the surface of the cloth in sufficient numbers to produce an unpleasant handle and appearance.
There is no simple solution to the problem of pilling. In the textile industry, polyester fibers are produced as medium- and high-tenacity filament yarns and as staple fibers of various lengths and fiber color to suit the kind of spinning machinery found in the textile trade. Staple fibers are usually drawn to give medium tenacities, but may be spun from polymers of lower average molecular weight to give improved "pilling" performance at the expense of some loss in abrasion resistance. Also, the finisher may reduce the pilling propensity of a fabric by the removal of protruding hairs from the surface of the cloth and by heat treatment to reduce the tendency of the fibres to migrate within the yarns.
These are all solutions to the problem of pilling applied by the textile industry. Solutions to this problem that can be applied by the end user of polyester fabrics have never been suggested, and the consumer still find pilling to be a problem that is encountered when wearing polyester fabrics and garments.